It is generally believed that, merely by walking slower, one can be safer and more stable. Contrary to this general concept, our recent computer model simulations showed that, at the onset of a slip, a slower velocity of the body center of mass (COM) may actually decrease stability and thereby lead to a backward loss of balance. A faster moving and/or a more forwardly positioned COM at slip onset can quickly carry the person forward to catch up with his/her slipping foot, thus avoiding a backward fall. Paradoxically, these findings suggest that age-related slowness in gait, rather than being safer, may actually predispose older adults to falling, accounting, at least in part, for a higher fall incidence rate among older adults. One possible mitigating factor, however, is that older adults can potentially compensate for the instability due to slowness by shortening their step length, thereby shifting the COM forward with respect to the base of support. The extent to which older individuals compensate for slowness-related gait instability is largely unknown. Successful recovery may, to some extent, rely on reactive stepping, although our preliminary findings indicate that such stepping fails more frequently in older than in young adults. Nevertheless, our preliminary findings also indicate that, after repeated exposure to induced slips, young and older adults avoided falling by improving their stability at slip onset through a forwardly shifted COM and an increased velocity. Thus, successful proactive behavior (e.g., changes in COM position and velocity to improve stability) can reduce or even eliminate the need for a reactive stepping response. In the following 3 stated aims, we are pioneering a line of research to investigate these issues, while exploring the mechanisms for effective intervention to reduce incidence of slip-related falls. Aim 1: We will test the theorized relationship between gait stability and the risk of slip-related falls. Aim 2: We will determine whether an age-related increase in slip-related fall incidence is attributable to a decrease in gait stability and/or to differences in the reactive response to a novel, unexpected slip. Aim 3: We will determine whether older adults decrease their fall incidence after repeated exposure to slips by improving gait stability and/or by enhancing their reactive responses.